1. Field of the Invention
The present invention relates to highly efficient lamps. More particularly, the present invention relates to a high power lamp which includes an envelope and exterior electrodes.
2. Description of the Related Art
High power lamps are used for illumination applications beyond typical incandescent and fluorescent lamps. One type of lamp known as a high intensity discharge (HID) lamp consists of a glass envelope which contains electrodes and a fill which vaporizes and becomes a gas when the lamp is operated.
Recently, a patent issued for a high power lamp that utilizes a lamp fill containing sulfur or selenium or compounds of these substances. U.S. Pat. No. 5,404,076, issued to Dolan, et al., and entitled "Lamp Including Sulfur" discloses an electrodeless lamp utilizing an excited fill. The Dolan, et al., U.S. Pat. No. 5,404,076 is incorporated herein by reference.
Projecting systems are used to display images on large surfaces, such as movie or television screens and computer displays. For example, in a front projection system, an image beam is projected from an image source onto the front side of a reflection-type angle transforming screen, which then reflects the light toward a viewer positioned in front of the screen. In a rear projection system, the image beam is projected onto the rear side of a transmission-type angle transforming screen and transmitted toward a viewer located in front of the screen.
In prior co-pending U.S. patent application Ser. No. 08/581,108, entitled "Projecting Images," to Knox, filed Dec. 29, 1995, there is disclosed a method of displaying an optical image by projecting the image along an optical path and at an optical device interposed across the optical path, at one time reflecting the image from the optical device and at a different time permitting the image to pass through the optical device to be displayed. U.S. patent application Ser. No. 08/581,108, filed Dec. 29, 1995, is incorporated herein by reference. A projection system for such a display is disclosed in U.S. application Ser. No. 08/730,818, entitled "Image Projection System Engine Assembly," to Knox, filed Oct. 17, 1996, which is hereby incorporated by reference.
The image source for a projection system employs a light that must be of high intensity and preferably very efficient. Such a light is disclosed in U.S. patent application Ser. No. 08/747,190, entitled "High Efficiency Lamp Apparatus for Producing a Beam of Polarized Light," to Knox, et al., filed Nov. 12, 1996, which is hereby incorporated by reference. If an optical image is to be displayed by projection, it sometimes passes through an optical device interposed across the optical path. In the projection system of prior co-pending application Ser. No. 08/581,108, filed Dec. 29, 1995, one or more optical devices reflect the image at one time from the optical device and at a different time permit the image to pass through the optical device to be displayed. There will be a decrease in light intensity once the optical image strikes the optical device interposed across the optical path.
While the lamp disclosed in U.S. Pat. 5,404,076 is very efficient, it was intended for a general lighting environment, not for a projection display system. As such, the design would be inefficient, so a more efficient design of the lamp is desirable for other environments, including projection display systems.